Free HD out of thin Air?

 

The DTV Blues?
The DTV Blues?

Yes its true that you can receive pristeen digital  High Definition video off the air for free….  or not!

HDTV has been around for years, but its only been since the digital video compression alogrithms got better that the FCC finally mandated that the transition will take place next February 17.

The good news is that if you live on a mountaintop – or othrwise have a clear line of sight to the transmitter site(s) you probably can easily receive a nice clean digital HD signal.

And it can be quite impressive!  All the local stations here in the Tri-Cities area are now broadcasting digital signals in addition to their old analog signals.  But unless you receive your TV via cable or satellite,  you need either a high definition TV or a converter box to receive the digital signals.   And if you want to receive these digital signals off the air, you probably will need an outside antenna.   Sounds simple, right?  Well…. not quite!

Three of the local channels have their transmitters atop Holston Mountain.  Many areas in the Tri-Cities have a line-of-sight shot at Holston, but there are enough medium-sized mountains around – Buffalo mountain, Chestnut Ridge, Bays Mountain to name a few – that huge swaths of the area may not be able to get the digital signals to work. 

The conventional wisdom is: “Its digital…. it either works or it doesn’t!”  Well ….. not quite!  When I first saw the clarity of HDTV over the air, I figured if it was available for free, I ought to avail myself of it!  I don’t watch that much TV anyway!  I also discovered that both cable and satellite’s versions of HDTV are, well, less HD than the off-air HD signals!  So why pay $50 or more per month for something I don’t watch that much of anyway?

I happen to live in the shadow of Chestnut Ridge.  Its a good 5 miles away, but it still keeps me from a clear shot to Holston, which is about 27 miles away.  That means the signals from those three stations are being “knife-edged” over the top of the ridge.  That means things like the season (leaves on the trees or not) and the weather – wind blowing or rain or snow – greatly affect the signal.

The FCC and the broadcasters have worked together to provide a <a href=”http://www.antennaweb.org”> site</a> to help you figure out where to aim  your antenna, and what stations you can receive.  You enter your address and it will even draw you a map!  The site’s software is actually quite good, being based on 3D terrain maps and station propagation data.  I discovered much later in the game that you can access some additional options – like being able to enter your antenna’s height above the ground – that greatly affect the results!

At first I tried using a traditional TV antenna – which had a corner-reflector for UHF and longer elements for VHF.  I discovered that the stations were all assigned DTV frequencies in the UHF band (much more on this below!) and I found that aiming my old antenna was very touchy, so I went out and bought a new amplified UHF antenna specifically made for DTV by Philips.

I was shocked to discover that the directions that come with it don’t tell you how to aim the darn thing!  Almost all antennas have some directionality, but it was only after hours of experimenting that I discovered which direction has more sensitivity.  (In case you’re wondering, the arrow in the picture above should point to the transmitter!)

It soon became obvious that I needed more height, so I used a 30-foot push-up pole I had and mounted the antenna on top of that.  That put the antenna just above the treetops in my yard, but they still can interfere with the signal if the leaves are wet or if the wind is blowing hard.

But here’s where it got even more complicated.  Of the three stations on Holston, two are a stone’s throw from each other, but one, WCYB is almost 5 degrees further north.  Even that small difference made it so that I could find a position to aim the antenna where channel 5 worked but not 11 and 19 or vice versa!   And that doesn’t even take into account the Fox station on 39 or the PBS station in Norton on 47!

Whats even worse is that the PBS station comes in clearer with the antenna oriented horizontally instead of vertically.  So that leaves me having to go out on my deck and turn the antenna in one of 4 different directions depending on which station I was trying to watch!  Somehow this doesn’t seem to be a great technological improvement!

Whats further confounding – in the analog days you turn the antenna to get the least amount of snow.  Now signal strength is meaningless.  Instead you watch a readout that is the error rate.  A “stronger”  signal display means that fewer errors are being corrected.

OK now heres the part I really don’t understand.   Now that I’ve finally got the hang of all this…  I’m told that some of the VHF stations have applied to broadcast their digital signal on their OLD ANALOG VHF channel!  The whole point of all this was that the FCC wanted to “free up” all that spectrum and sell it to the wireless carriers!  Which they did!  So now that I’ve got my setup sort of working with all the UHF signals, at some vaguely defined moment, they will switch back to using their VHF channel – but it will be digital!

So there really are TWO DTV transition dates!  Phew!  I think I’ll just watch TV on my laptop via the Internet!  It doesn’t stutter to a halt everytime the wind blows!

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